The present invention relates to interconnections made between a multi-layer printed circuit board and a high speed coaxial connector. More particularly, it relates to a printed circuit boardxe2x80x94connector combination for establishing contact between a printed circuit board and a coaxial cable. The invention provides control of signal line impedance by minimizing the length of the ground path through the connector, thereby maintaining the integrity of the high speed signals traveling through the connector.
The interconnection of integrated circuits to other circuit boards, cables, or other electronic devices is well known in the art. Such interconnections typically have not been difficult to form, especially when the circuit switching speeds (also referred to as signal transition times) have been slow when compared to the length of time required for a signal to propagate through a conductor in the interconnect or on the printed circuit board. However, as circuit switching speeds continue to increase with modern integrated circuits and related computer technology, the design and fabrication of satisfactory interconnects has grown more difficult.
Specifically, there is a growing need to design and fabricate printed circuit boards and their accompanying interconnects with closely controlled electrical characteristics to achieve satisfactory control over the integrity of the signal. The extent to which the electrical characteristics (such as impedance) must be controlled depends heavily upon the switching speed of the circuit. That is, the faster the circuit switching speed, the greater the importance of providing an accurately controlled impedance within the interconnect.
Connectors which have been developed to provide the necessary impedance control for high speed circuits are replete in the art. For example, U.S. Pat. No. 6,024,587 discloses a high speed circuit interconnection apparatus for providing electrical connection between multi-layer printed circuit boards. The art teaches that an optimum printed circuit board interconnect design minimizes the length of marginally controlled signal line characteristic impedance by minimizing the physical spacing between the printed circuit board and the connector. The art also teaches that connector designs which involve relatively large pin and socket connectors with multiple pins devoted to power and ground contacts provide only marginally acceptable performance for high speed printed circuit boards.
Unfortunately, currently available high speed interconnect solutions are typically complex, requiring extremely accurate component designs which are very sensitive to even small manufacturing variations and which, as a result, are expensive and difficult to manufacture. What is needed is a printed circuit board interconnect system which both provides the necessary impedance control for high speed integrated circuits, while still being inexpensive and easy to manufacture.
The present invention describes an interconnection system for connecting printed circuit boards and high speed coaxial connectors in an economical manner. The electrical connector assembly includes a printed circuit board having signal and ground traces, with the signal traces connected to signal contact pads and the ground traces connected to a ground contact pad. The ground contact pad is positioned adjacent an edge of the printed circuit board. A pin header is connected to the printed circuit board signal contact pads. The pin header may be a surface mount or through-hole pin header, or any other suitable pin header known in the art. A connector for receiving the pins of the pin header includes coaxial cable terminations which have a contact beam for contacting the ground contact pad adjacent the edge of the printed circuit board. In this manner, the lengths of the signal and ground paths are minimized through the interconnection, thereby providing improved connector performance in high speed systems.